Radio control system



My 10, 1949. H. H. ABBOTT ETAL l RADIO CONTROL SYSTEMV 4 Sheets-Sheet l.

File'a Feb. 23,1946

A 7' TOR/VE V May 10, 1949. H. H. ABBOTT Erm. '2,469,539'

RADIO CONTROL SYSTEM Filed Feb. 23, 194e l 4 sheets-sheet 2 L F/GZ hf H. ABBOTT /NVENTORSJ hf M. BSCOM B. FAIRLMB A TTORNE Y May 10, 1949. H, ABBOTT E1- AL 2,469,539

'RADIO CONTROL SYSTEM Filed Feb. 23, 1946 4 Sheets-Sheet 3 f Has Ar Tom/5v H. H. ABBOTT EI'AL RADIO CONTROL SYSTEM May l0, 1949.

Filed Feb. 2s, 1.946

RAD/0 RECEIVER 4 sheets-sheet 4 v I H. H. ABBOTT H. u. BAscou e s. FAI/PLANE *wir-v ATTORNEY Patented May 10, 1949 RADIO CONTROL srs'rlnvr- Henry H. Abbott,;Yonkers, and Henry M. Bascom,.

New York,4` N. Y.,` and Preston. Fain-lamb,-

Butler, N.

Laboratories, Incorporated, t New corporation of ,New York J., assignors to Bell-Telephoney Application-February 23, 194s,.seria1.No. 649,582;

Claims.

ling, overa aline, the operation of selector vapparatus located at rtheseveral. radiov stations to connect the input vcircuit of any; desired one of. a plurality of radio transmitters rto av-common communication channel `terminating at the master station.

Another feature residesv inc means including said code transmitting apparatus and selectors for selectively conditioning the selected radio transmitter to transmiten :any .desired `one ot Aa predetermined plurality of.- firequency hands.4

A Afurtherfeature resides inimeans also including said `code.transmitting apparatus andsselectors forselectively vconditioning desired ones of said vradio receivers 4to respond to desired ones of a predetermined plurality of lradio frequency bands.

A still further feature .resides `in means including `said .'code. transmitting "apparatus and selector iior selectivelyand individually:disconnecting desired ones of said receivers -from the.V communication channel.'

Still another featurefrelates to insuring reliable operation of `the system yloy requiring the transmission 'of .two successive codes, ina predetermined sequenceto enect the desired control thus. obviatingfalseand. improper control of station. and frequency selection dueto yfalse line impulsesv vcausedlzeyl accidental 'line grounds and crosses,v crossesiwithv other electrical circuits, false relay. operation, etc.

Another feature I resides in `means alsoV controlled vby said fcode transmitting lapparatus `and selectors,A responsive to '.energization of a -telephone transmitter associated with the communication .channel at the .fmaster station, vfor causing the radiation of :theradio signals from .the selected radio-transmitter v4and vdisabling .allradio receivers connected toxthe .channel 4and responsive to the'deenergization of .thetelephonetrans- 4mitter for :deenergizing the selected :radio 'transmitter and yreenaloling all.- vconnected receivers.

Other` features :fof the .invention -Will be Aapparent from the'followngdescription: when read `in connectionr -rvithf- :the accompanying \..,drawings z.

Figs.; 1 :and'32 "of-Which1 Whenxplaced sidesby side 'with .Fi-gr, lvtocltheleft auf FigrT-2g`ishowthe arrangement fofy apparatusa'and circuit yat a ymas-- ter or Acontrol )station fconnected -over fa-;.Dai1*` -0`f lines to a plurality (six-' "ot :distant :radio fstatio'n locationsfltwo .of fwhi'ch';- stationsA I fand: 6 le are shown *on* Figs. `Branded:I

Referring 'to the`A dralvving,iFi`g. l shows antelephone .for Y. use by 1an attendant ',(dispatcher) 'lat the master: or control-statiun, a.`,pl1.1rality `of groups of selecto r fkeysiforrselectively initiating they .desired )control int `zthesdesired radio station, and :a :start-stop code-t transmitting distributor. Fig.v 2 vshows-the relay 4equipment vat the master station fassociatediivwithithe"distributor :shown I:in Fig. 1 and :Figse andrei V`show. a .-.nonz-.typing;;selector" at one of f the stations `(stationfrl A) and circuits therefor; to:v control afxrcombinedrg-.sradio transmitter and receiver. v`.in accordance 'with codes A.transmitted :from: thefmaster stations. An additionalsstation -,6 ofthesystem, similar .fin-:al1 respects toftheerst station, lis indicatedoinz; the upper right-hand corner of Fig. 4.

In describing the operation -of ithe'fsystern, :from which an. understanding, of the *1 inventionr Imay obtain, it .wi-1lrbe Yunderstood .that .the attendant' i..e., the dispatcherfs telephone `:atfthe masten-or control .station isv adapted to -beconnected sto-a speech communi-cation :linelsy yWhic'h-'i-extends to a plurality ofwdstant radio .stationalocations--as for example, .stationsl V:and Brshown; in Figs. 3 and "4, -anclthat the .output circuit .of the: radio receiver at ,each-offthestations is .connected 4.to 'line L3 and one of ,thereceivera .for example at station ,I is vconditioned tol; receive .on :one --oi the frequencies for ,which Vit `is adapted, `Vfrequency l for example, ,whereby the attendant ,is.ab1e to monitor on vthe line, i.' e., listen.

Now let it be assumedithat .theldispatcherr after listeningpnrthe `vline, ,desires to 'transmit from the transmitter at station I"'on vfrequency, TRI He therefore selects/the vdesired radio `transmitter by depressing thegtransm'ltter rselectingkey Sl which-locks, andzselectsthe vdesired 'transmitting frequency 'by depressing the yfrequency lkeyu TF! and, thereafter, frnomentarilyY operates thefnon- Alocking code start Lkeyl TST""(Fig: 2): 'whereupon relay-TS operates 'in a-circuit from battery,^wind ing lof- `TS; right-:handf' contactsI of Y'TST,jcontact l of receiver start'fkey'RSTLthrough similar contacts -of 'the-receiver vstart `-keys 'for receivers 2 to '5, .'inclusive, vas'indicated'hytheebrolren line 2; contac'tl3'of receiverfstart rk'eyrRS'I,L and contact i4-of relay: Gtofgroundr '.'R-,elay Ts'foperates yand-:closes its contacts' 5f ov operate relay-W; -o`f battery, resistance 6, winding of W and contacts 1 thereof, contacts 8 of relay G, contacts 5 of relay TS and contacts 9 of relay I0 (Fig. 1) to ground. Relay Z is short-circuited at this time by the connection of ground to both ends of its winding. l

Relay W in operating closes its contacts II to complete a locking circuit for itself from ground, contacts I2 of relay PW contacts I3 of relay PZI, contacts II and winding of W and resistance 6 to battery.

Relay W also closes its contacts I4 to close a holding circuit for relay TS which is completed from ground over contact I2 of relay PW, I3 of PZI, contacts I4 of W, lower front contacts and f winding of TS to battery. Further, relay W closes its contacts I5 to operate relay G in an obvious circuit. Relay G in operating closes its contacts I6 to operate the release magnet I1 of the distributor D (Fig. 1) in a circuit from ground, contacts I8 of W,.contacts I9 of relay Z, contacts I6 of G and winding of magnet I1, whereupon the stop latch of the distributor, which normally holds the distributor brush 2I in contact with the stop segment 22, releases the brush and it starts to revolve under the influence of motor 23 which it will be assumed is in operation but prevented from rotating the brush shaft due to slipping of clutch 24. When the brush 2| leaves stop segment 22 and passes onto start segment 52, which'latter segment has no connection to the key and relay equipment at the master station, ground is removed from relay I0 which relay thereupon releases and opens its contacts 25 thereby opening the normally closed telegraph or signal line 'IL'which serially includes line battery LB and during the interval the brush is passing over segment 52, the line 'IL remains open and the receiving magnets associated with the selector at the various dis-tant radio stations, such as magnet R at station I (Fig. 3), releases.

Release of relay I6 also opens its contact 9 thereby removing the ground previously applied to the left-hand end of the winding of relay Z and this relay thereupon operates in a circuit from ground, contact I2y of relay PW, contact I3 of relay PZI, contact II of relay W and winding of Z and resistance 3| to battery.

Now if the code required to select the transmitter at station I requires a marking impulse during the contact of the distributor brush with segments 26 and 21, then leads 26 and 21 from the distributor will be connected to terminals 32 and 33 of key vSI of the row of transmitter select keys and in like manner if the code required to condition the transmitter at station I, to transmit on the desired frequency (TFI) consists of two marking pulses caused by contact of the distributor brush 2I with segments 26 and 28 then lead 26 will be connected to terminal 35 of transmitter frequency key TFI and lead 28 will be connected to terminal 56. Further terminals 36 and 31 of key SI will be connected to terminals 38 and 39 of relay TS (Fig. 2) and terminals 43 and I3I of key TFI will be connected to terminals 44 and 5I of the same relay.

Other connections, in Various combinations, between the distributor D and the terminals of the other select keys of Fig. 1, and between these keys and switching terminals of the relays of Fig. 2, will be made to transmit over line TL, the characteristic codes required. as hereinafter discussed, to effect the desired controls which will be understood to those familiar with teletypewriter systems.

Now continuing with the description of the operation of the system, when the distributor brush, now in motion, moves off segment 52 and makes contact with the ilrst transmitting segment 26, ground is applied thereto and an energizing circuit for relay M is closed over lead 26, terminal 32, closed contacts 45, and terminal 36 of key SI, terminal 38y and contacts 46 of relay TS (Fig. 2), contacts 41 of relay W, now operated, and winding of relay M to battery which latter relay now operates and recloses the line TL, Which was opened when relay I Il (Fig. 1) released at the beginning of the code cycle and reoperates the selector magnets such as R at the different stations, which magnets control the closure of contacts of the selec-tor.

During contact of the distributor brush with segments 26 and 21, relay M remains operated, and the line TL closed, thereby transmitting the predetermined code for which the selector S is adjusted, thus closing its contacts 53 which operate the transmitter start relay 54 at station I which relay opens its lower back contacts and closes its front contacts in preparation for the next code transmitted which determines the frequency on which the transmitter is to operate. Operation of relay 54 closes an upper contact to prepare a circuit for relay 55 when relay 56 is energized. When the distributor brush moves 01T segment 21, relay M releases thereby opening the line TL and when the brush completes its first revolution, and engages the stop segment 22, relay I operates which closes its contacts 25 to again close the line TL. Relay I0 also closes its contacts S to connect ground over contacts 5 of relay TS and the front contacts of relay Z to short circuit relay W which thereupon releases. Release of relay W at this time, however, does not open the circuit for, and release, the latch magnet I1 associated with the distributor for the reason tha-t an alternate circuit for magnet I1 is closed at contact 51 of relay W and contact 58 of relay Z. Further the release of relay W does not open the holding circuit of relay TS due to the operated condition of relay Z.

Due to the continued energization of relay I1, the distributor does not stop at this time and as soon as the brush moves o start segment 52 another code is transmitted to operate the selector at station I to adjust the transmitter thereat for the desired frequency, as determined by the operation of transmitting frequency key TF1 which codes consist of an impulse when the brush passes over segment 26 and another when it passes over segment 28, relay M being .controlled at this time over contacts 59 and 60 of relay TS and contacts 6I and 62 of relay W now released. When the distributor brush moved off the stop segment 22, relay I6 released thereby removing the ground which had been holding relay Z operated and this relay then released thereby releasing, at its contact 16, the holding circuit for relay TS which released. Sending the transmitting frequency code on'the second revolution of the distributor causes the selector S at station I to close its contacts 63 to operate relays 64 and 56 over back contacts 66 of relay 61 and front contact 68 of relay 54, lower winding of relay 64 and winding of relay 56 to battery. Relay 64 opens its upper back contacts to release any succeeding relays which may be operated and by closing its upper and lower front contacts locks itself over its upper winding and the series chain 1 'strapped togetherrv andlconnected *to-relayy |30 riot lowermcontactst;tofrbatteryifontheinneiidower armature of relay 69. Operation of relay Sura-lso .':closes its loWermostf-contact;therebymconnecting .1: .mitter-v to transmit 'on thedesired.frequency-g` i: e., 5

Operation of relay 56 completes afcir-euitlto 'operate vrelay; 55 which h'-wasprepard-'ff'byllthe .t operation of'-.re1ayI 54.

Relay `55V closes its'contacts :toricalca-itselfY oper-.I l0'- Lated... under -control'-y off-:relaysl'f431'r andSiBS. Oper- ;.ation of relay =55also'.fconnectsltheilinputf-of the .ztransmitt'erito' the lineLIiand byfclosingli-tsconlwhereas'- contacts 153 "are" connected Ato relayL 54. While Anot shown it Will-belunderstood"thatfat station 2, for example,fcontacts '|'251-fwillf-beconnected toftherelay at that'stat-ion'corresponding,,25 llto'l relay* 54 land the contacts-*53, -'|26,"'|21,""|28 and `i|29-wil1ebe strapped and connected' tothe relay correspondingto=irelay1"'l30. "-Atf station' 3, @contacts I 26 will' be'fconnected to the' relay `54 1 and so on.

It will therefore'be obvious'that' Whenar' code 2: is' 1 transmitted; to closefcorrtacts *53' at station l, corresponding'contacts at 'the otheristations' will be Iclosed to -operaterelays'tcorrespoirding" to relay |30 and'when theI succeeding-"codeWasvf35 transmitted, it' closedcontacts63"andr operated relay v|54, and vsimultaneously this` sameL 'code will also voperate` selectory contacts corresponding" to 1.1.63 atl station 2,iand succeedingfstations;'andf'due --to the *factv that the `relaysof tl'reseother"sta-"40" tions, correspondingto-relay-54arenotoperated circuits at the vother stationswillrbe completed -over back contacts` of' 54' and: front' contacts' bf "relays |30 to` operate the"corresponding"release, relay 13 Which-Will*rel'easerelay'55;fifope1atedfi4 and disconnect and disable the 'tran'smitter `which at-the ltime is'--connectedlt-1ine L.

It willv now be understood 'th'atithe selection A'and connection to the `line ofthe-desired ,trans-,iz r ymitter has" been eifectedxand .also the. trans-00' f mitter has'beenconditloned'stotransmit onfr'eyquency f. Now `when"the""distributor completes its second revolutionv and the brush engages the -stop segment 22;*ground `Will-'be'a'pplied'tc` relayy "#16 vwhich operates*and'closes` its"'contacts'"25"555 :to close'the line'fTL,` as` previously "described RelaysWand Z are now released which'fwas their `.original condition.

. .Receivers at 'stationsr and 6 set 'to receive .on frequencgfyz aiclosesf.alcircutLtor.operaterrelayiRSii whichzeis '.f'ztraced.lfromtzb'attery :winding toifsRSL.: contacts E .1 1. of key RSTlpcontacts: 3 :off :keyl 'RST6,"..before '"thisrkey. is -,operated-.to` ground over contacts4 of relay G. Relay RS1 in operatingY .closesits contacts .78 to operate relay-W inV a circuit from fgroundefover. contacts-.9.0i .relay i0, conta-cts. k18 .cfr relay :RSL andzcontacts 8 .of `relay G. and` con- ;tactsl 1': bfsfrelaylfW. Re1ay inv voperating .locks itself'.: and relay.. RSi :toi groundl over. contacts f :i 2 of relay PW and operates relayG thusenergizing the latchmagnet l1 of the distributor, where-l' upon 'the'distributor starts to revolve and sends code; pulses overthe line TLas determined by :the receiver -frequency key noW operated. From this-.point on the operation isthe same as before described for. .sending the transmitter selection Aandtransmitter.frequency code, i. e., onthefrst revolution of the @distributor ,ground Vfvvill-be applied-to.certain-:upper lcontacts of: relayf=RS1,

-determinedfbythe operated keyfRFaandv the wiring therefrom to the relaycontacts which will control the relay M over the front left contacts of -relay Wznow operatedand on the second revo1ution,vatfwhich .time relayvW4 is released as previously4 described, a4 diierent` code will be transmit-ted as determined by. the Wiring. beitween. the :key RFz and the lower.v contacts. of

relay::RS1.

`The first code-sent, onftherfrst .revolutioniof the distributor, 'We will assume. vactuates these- :lectorfatstation' to close .its'contacts .1 Qthereby operating relay B1 Whichinfoperating'iclosesits left-hand' contacts in preparing for. the immedievately .following icode which we iwill 1 assume causes the selector to close its contacts 8U thereby .completinga circuit .tooperate relaytl` in a .circuit Y including: contacts 82 yof relay B'Iwand xrflowerfwinding. of vrelay 8| to battery.

Relayu 8| 'operates' and opens at its -contacts 84;the'locking circuit for relay 85, which we have v.assumed 'was previously operated to condition the .receiver `fatfstaticn to receive on frequency f1. vvRelay lithereupon locks over. its inner front rrcontactsxandl by closing'iits ycontacts 86 connects groundVover' conductor' 31, to the radio receiver which y,winx-perform the necessary switching functions: tol condition itto receive on the de- :siredlfrequency f2' and to transmit lthe -received .signalsitolthedispatchers'-station over line L.

",'I.he'..samev operation as just described is also :effectedffatistation'i 6, the circuits ofwhich are :-not-,shown.

After the distributor completes its second revo- ;lutionfit stops -as before described andthe line Tlfisnow closed and-relaysW and Z are 'in their normal released condition.

-Itfwill be noted from lthe foregoing'that after theproper transmitter selection code impulses ilficocaretreceivedf at 'the station thereby operating slow-release relay 54, no operationl of relay'55 .lis'ieifected unlessthere immediately follows; before= 54'releases, a frequency selection code'to operate one of the-transmitting frequency relays fsuchras' 64,5f"|`|8,etc., which relays are controlled 4over the front contacts of relay 54. Relay 56 @operates :in series with anyone ofthe transmit- .tinglr frequency relays and closes a circuit to operate.-relayi 55 `provided relay 54 is operated.

`lurther, in case Ythe dispatcher desires to controlfany receiver :frequencyv at a" particular station; the'operation of any one of the receiver fre- :iquen'cykeysf'of the desired stationcausesaiprevdeter:'nin'ed code mbe-transmitted toclose a' contactrat thestation" to-'operate a'r'elaysucliasl '61 at station which is .slow-releasing. Following this code a second is immediately transmitted and if it is received before relay 81 releases, the desired frequency receiver relay such as 85, for example, will be operated.

In other Words, high reliability of the system iS assured by requiring the receipt of two sets of selecting impulses in the proper sequence within a predetermined short time interval before a desired connection is effected or an established connection is changed.

Dispatcher operates "press to talk key With the radio transmitter at station connected to the line L and conditioned to transmit on frequency f1, and the corresponding receiver conditioned to receive on frequency f2, the system is now ready for communication and the dispatcher then actuates the press to talk key 'I6 associated with his telephone set, thereby closing the circuit from battery through the telephone transmitter and relay 88 to cause that relay to operate thus closing a circuit to operate relay 89. Relay 89 opens its lower contacts 90 and closes its contacts 9| thereby short-circuiting the rightliand winding of relay PZ and operating relay PW which relay operates and locks and also closes at its contacts 92 a circuit to operate relay G which relay, in operating, closes its contacts it to operate latch magnet |1 thus starting the distributor and thereby releasing relay i9 when the brush moves oi segment 22. This opens the line TL and removes the short-circuit from the righthand winding of relay PZ which relay operates and holds to ground on the left front contact of PW.

Relay PZ closes its contact 93 to operate PZi which locks, opens its contacts to open the circuit for the latch magnet |1 and also closes its contacts 94. If We assume that segment 29 is connected over lead 20 to terminal 95 associated with contacts 94, when the brush engages segment 26, relay M will operate to close the line to send a single pulse to operate selector magnet R and close contacts 96 of the selector. Prior to the transmission of this pulse, relay 48, which is in series with magnet R in the line TL, releases during the open interval of the line and due to the fact that relay 55 is operated at this time ground, over its contacts 14, is connected to the windings of slow-release relay 49 which thereupon operates and closes a circuit from ground, contact 1| of relay 49, contacts 91 of relay 93, contacts 99 of relay |09, and contacts |01, to energize the radio transmitter and put the carrier frequency on the air. This operation provides a very rapid energization of the transmitter at the first movement of the distributor, i. e., as soon as the distributor brush engages the start segment 52 and opens the line TL. Now when the line is yclosed by the first code pulse, relay 48 operates at the same time as the selector magnet R thereby opening the circuit previously closed to operate relay 49 and this relay is deenergized, but as its slowrelease characteristics are such that it holds for a short interval, during which time the selector contacts 90 are closed to operate relay |00, this relay locks and closes its contacts |02 thereby completing the holding circuit to maintain a ground connection to conductor 15 to keep the transmitters on the air. This circuit may be traced from ground, contacts |03 of relay 49 released, contacts |02 of relay |00 and contacts |0| of relay 55. Release of relay 49 after relay |00 operates completes a circuit to operate relay 98 whichA accomplishes'noV useful function at this time.

When the distributor completed its revolution and stopped due to the release of latch magnet |1, relay I0 reoperated thereby connecting ground over contacts |04 of relay PZ to hold that relay operated.

As long as the press to talk key 16 remains operated, thus holding relay 89, relays PW, PZ and PZi remain operated at the master station.

At station l when relay 49 operated in addition to energizing the transmitter to put its carrier frequency on the air, this relay also closed contacts |06 to connect ground to conductor |01 to disable the radio receiver and when relay |00 operated and relay 49 released, a substitute circuit was closed to hold ground on conductor |01 to keep the receiver in stable condition. This can be traced from ground, contacts |09 of relay 49, contact ||9 of relay |00 to lead |01.

The radio transmitter at station is now on the air and the corresponding radio receiver is disabled. The dispatcher at the master station now talks over the line L and the speech signals are transmitted from the antenna. At the end of the speech transmitting interval the dispatcher releases the press to talk button 16 thereby releasing relay 99 Which closes its contacts 90 thus shunting relay PW by connecting ground to the right-hand terminal of its Winding which can be traced from ground, contacts 9 of relay l0, contacts |04 of relay PZ and contacts 90 of relay 89 to the right-hand terminal of relay PW. This latter relay therefore releases and closes its contact |`2 thereby operating relay G which closes its contacts I8 'to operate the latch magnet |1 of the distributor. This can be traced from ground, contacts of relay PW, contact ||2 of relay PZ, contact |6 of G and winding of magnet |1 to battery. Latch magnet in operating releases the distributor and when the brush moves oi segment 22 relay l0l releases thereby opening its contacts 25 to open the line TL and by opening its contacts 9 releases relay PZ which closes contacts ||3 thereby connecting relay M to a predetermined segment of the distributor, for example, 28 by Wfay of terminal ||4 of relay PZ, whereby a single pulse is transmitted over the line TL when the distributor brush passes over segment 28. Relay PZ in releasing also opens its contacts ||2 thereby releasing the latch magnet |'1.

When the distributor completes its revolution, it stops on segment 22 and relay I0 reoperates thereby shunting relay PZ1 in a circuit to ground from contacts 9 of relay |0, contacts ||5 of PZ to the right-hand winding of terminal of PZ1. This relay now releases and releases relay G. Relays PW, PZ and PZi are now released in readiness for another operation cycle.

When the line TL was opened at the start of the distributor relay 48 at station released thereby reenergizng relay 49 which operated, thereby opening contacts |03 to remove ground from the transmitter control lead 15 and also reopens its contact E99 to remove ground from receiver control lead |01 which thereby reenables the receivers.

When the last-described line pulse, caused by release of the.press to talk key, is received, it will be assumed that it causes selector S to close its contacts |6 thereby short-circuiting relay |00 which previously had been operated and locked. Relay 48 reoperated at or before the first operation of the selector magnet R thereby deenergizingrelay 49 which starts to release and nally encaisse closes sits :bottom-1 contactl fatsor before'.- relay fI 00 I.

releases'- thereby completing azcir'cuit to-cause the release of relay 98. fromwground; contact-.1I II of relayy I00,l lower backicontactifof Yre1ay:49=to the vright-hand terminaliofrthe:windingfof 'relayf 98 :which relay now releasesiandrestores thi'spart ofthe station-circuitfixe., relays |00, 139 and 98 to normal.

ChangeP l transmitting Vfrequency If the-dispatcher 'desires-to transmit on a differentfrequency 1 than the'v oneA originally selected, for example 'f2 lh`e--will depressA transmitting frequency: key TFi which-locks and automatically releases-key-Tli` Transmitting-start key TST is then operated thereby starting anoperation cycle to again transmit` inthesamemanner as before described-,ifawpulseJ code-determined by the v'still operated lkey'Si of the-row of Vtransmitter select keys'lto-cause-ithe -distributor to control thesele'ctor at-station'I toagai-n close its contacts 53 to'foperate .relay fand-*to' immediately thereafter vtransmit the pulse code determined by the operationfoftransmitting frequency key TF2 to control C the station `selector to close its Contact 80''lto Y -operate transmitting frequency relay I I0 in series with"relay156-Which, however, performs no usefulfunction ifwe 4assume that relay 55'is stilloperated.z Operation of relay II8 opens itsv contact I I I9to open the-holding circuit for relay -64 lwh'ich'releases andfby'closing its Aupper backlcontact'wapplies vground'to lock-relay II8." Relay-@64 removesground 'from` conductor 'I0 and'frel-ayd I0 connects ground to conductor |20 thereby` changing thetransmitter to `transmit on frequency f2s Change :receiver frequency If on-thef other hand the dispatcher desires to chan'geth'ereceiver at'station-I to receive on the same frequency as that for-whi-chthey transmitter is=conditioned; i. e.,-J1, which it may be mentioned thereafter isends` the `code'to operate krelay 854 which releas-es relay 8| thereby" connecting ground to receiver: frequency lead I2I and removing ground from control lead 81 thus changingthe frequency at whichfthe radio receivernat.l

station- I responds:-

Disconnect the transmitter If the dispatcher desires to disconnect the transmitter from the line L at station I he will operate the transmitting frequency key OFF and hereafter actuate transmitter start key TST thereby initiating operation of relays TS, W, Z and G to cause the distributor to again transmit the code determined by the already operated key S1 which causes the selector at station I to again close its contacts 53 to operate relay 54 and immediately thereafter to send the code determined by the operation of the OFF key thereby causing the selector to close its contacts |22 to operate relay 69 which releases relay 64 to remove ground from transmitter frequency lead 'I0 to disable the transmitter and to release relay 55 which disconnects the transmitter from the line and to also open the carrier control lead 15. The dispatcher can now select and connect another Thishcircuit can be-traced 105i transmitter; ifrdesired, Tini: the manner originally-.r

described. t

Disable" receiver If-.the i dispatcherfdesiresn to disable any =radioy' receiver: :which mayl be in,receivingfconditioni` asv for example the -receiveras-station,A I he will press the OFF .key of the row ofreceiver frequency keys for-station-I and thereafter the `receiver start key ,RSTi to initiate two lrevolutions ofV th-e'di-stributore andthe transmission` -of. ya code tof-rstwclosese--- lector contacts 'I9 at station l and thereafterafl second code-to' close selector-tcontactsfl 22 to vlop",- erate y l'relay ,s I 2 3y ewhich;1 .relay -v opens 1v thel holding-tr circuit for relay;.which releases andy removesground :from:y conductor I 2 I'. Relay f I23,.- in'v opt-1in erat-ing-,f-lockstopens. its lowermost contacts fto re-l move ground-:+from :Mael-IWL` and :by closing its.,` uppermost-contacts `connects ground to conduclromftheeforegoingiv description it will be` seen.. that the system-ofthe Lpresent invention enables the dispatcher atl -the`- master f station to vcontrol by'means e of .the f code distributor, 4selectorv keys and'relay circiuts, any of the radio transmitters and to `disable' all of :the radio receivers duringth'ew:

interval l their` dispatchers @telephone transmitter isizenergizedrzi.:e;;"while he Iis talking;7 (e)` and *to restore-the;radio1-receivers to normal 'receiving-f1 condition and .to deenergize the lconnected radio' transmitter: (fr. to.; disconnect.r any* connected radiottransmitter:fromvathe; line 'and (g) `to dises able? l:any itconditioned 'iradid' receiver: i

Whatis claimedfis-z; r

1.l Ifra :i station selecting zsystem; in fcombina-A v -tion,r.a master station',"'a telegraph" line extendingff therefromgfa plurality of yradio stationszalongsaid? line',Y`eachfstationfcomprising :a :radio transmitterff" and fia t radio1-receiver,v each L of said f transmittersv being'K adapted .to beadiusted tatran'smit on 'anyf 'oneof apredetermin'ed inumberof' different 'radio 1 frequencies and eachreceiver beingadapted to be=e adjusted tozrespondto' any one ofa predetermined pluralityrof different received frequencies, acomi mori:communicatioirchannel extendingefrom' the'r e masterfstationf:tov Vall of vr"said lradio fstations; tele` graphf'.'selector'fapparatus;L in '/said "telegraph linee individual to the several radio stations, said telegraph selector apparatus adapted to respond to two successive and different codes initially, and start-stop permutation code transmitting apparatus adapted to transmit two successive and dierent codes initially, said code transmitting apparatus being selectively controlled at the master station and associated with the telegraph line for controlling said selector apparatus in diiferent manners to selectively adjust any desired one of the radio transmitters to transmit on a desired one of said` transmitter frequencies and to connect the input circuit thereof to said communication channel to the exclusion of any other transmitter, to disconnect any connected transmitter, to selectively condition a desired one of said receivers to resopnd to any desired one of said predetermined frequencies, to connect the output circuit thereof to the communication channel, and to selectively disconnect any connected receiver therefrom.

2. A system in accordance with claim 1, characterized by means for causing said code transmittingapparatus when started to complete two successive operation cycles and to transmit two respectively diierent codes and means at each substation responsive to the ilrst of said two transmitted codes to prepare for the desired selective adjustment and responsive to the second transmitted code to complete said desired adjustment.

3. In a station selecting system, in accordance With claim 1, in which said master station comprises an attendants telephone set connected to said communication line, said set including a telephone transmitter adapted to be energized and deenergized under control of attendant operated means, characterized by means responsive to energization of said telephone transmitter for causing said code transmitting apparatus to transmit a code to control the selectors in the telegraph line to simultaneously condition the radio transmitter, connected to the communication line, for radiov transmission and to disable all said radio receivers, and responsive to deenergization of said telephone transmitter to cause the code transmitting apparatus to control said selectors to simultaneously decondition the conditioned transmitter and remove the disabling condition from said receivers.

4. In a station selecting system in accordance with claim 1 in which said master station comprises an attendants telephone set connected to said communication line, said set including a telephone transmitter adapted to be energized and deenergized under control of attendant operated means, said start-stop permutation code transmitting apparatus being connected to the telegraph line to serve as a distributor after it has transmitted the codes to eect the desired selection at the radio station, said distributor being operated by the energization of the telephone transmitter and beingadapted to transmit an initial pulse,'means associated with the telegraph line and responsive to said initial pulse to energize the radio transmitter, and other means associated with said telegraph line responsive to said initial pulse to temporarily disable all said radio receivers and to simultaneously condition the radio transmitter, connected to the communication line for radio transmission, and responsive to deenergization of said telephone transmitterto cause a second operation of said distributor, said other means associated with the telegraph line, responsive to the respective pulse,

being effective to simultaneously remove said disabling condition from the radio receivers, and decondition the transmitter.

5. In a station selective system in combination,

a master station, a telegraph line extending therefrom, a radio station comprising a radio transmitter and a radio receiver on said telegraph line, a communication line between said master and radio station, a selector apparatus associated with said telegraph line at said radio station, said selector apparatus adapted to'make station and station frequency selections in response to two successive and different codes received over said telegraph line, switching means controlled by said selector for selectively and simultaneously conditioning said radio transmitter for radio transmission and for disabling the receiver, and for deconditioning the transmitter and enabling the receiver, a start-stop permutation code transmitting distributor at the master station adapted, when started, to transmit an initial open circuit pulse for conditioning said selector apparatus over said telegraph line, an attendants telephone set comprising a telephone transmitter at said master station, attendant controlled means for energizing said telephone transmitter for speech transmission, means responsive to energization of said telephone transmitter to initiate operation of said distributor to transmit a code to control said selector to effect said simultaneous conditioning of the radio transmitter and disabling of said receiver and responsive to a subsequent deenergization of said telephone transmitter to initiate the second operation of said distributor to transmit code pulses to effect deconditioning of the radio transmitter and reenabling the receiver, and other means responsive to the open circuit start pulse, transmitted by said distributor at the start of its operation for temporarily conditioning said radio transmitter and disabling said receiver or deconditioning the transmitter and enabling the receiver, depending on their previous condition, until the selector responds to the code transmitted.

HENRY H. ABBOTT.

HENRY M. BASCOM.

PRESTON B. FAIRLAMB.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,101,668 Bishop et al. Dec. 7, 1937 2,176,868 Boswau Oct. 24, 1939 

